Correlation filter design for classification of road sign by multiple optical correlators

We propose a new technique of correlation filter design for optical correlator. For detection and classification of complex patterns, ability of single optical correlator is not enough. To achieve high performance of classification, a multiple correlator is suitable in respect of flexibility in correlation filter design. We attempt to design a set of correlation filters for use in multiple optical correlators. As the target, we select road signs. In real scene, the scale and aspect ratio of road sign are dependent on the distance and angle of observation. In addition, many kinds of signs are used. Therefore the correlation filter set has to be designed as to have distortion invariance to adapt to the change of aspect and the variation of road signs. We apply the technique of multiple-object correlation filter, such as the synthetic discriminant function, to the design of correlation filter set, in order to obtain the necessary invariance. Me calculate 180 filters in order to detect and classify 15 kinds of Japanese road signs in real scene. Computer simulation result shows that the combination of multiple optical correlator with the correlation filter set can indicate high performance of pattern detection and classification.